66 Kl.l.l. Sysn:.\l II.CIIMC.II. JOi KX.iL 



filter stniituns havinn ilifTeri-nt iinpitlance characteristics hut the 

 same propagation characteristic is, therefore, of aci\'antagc. In the 

 attenuation range this is als<j true wiure inipctlance conditions are 

 imposed at the terminals of the filter. 



One class of structures which possess desirable image impedances 

 and whose characteristics are readily determined from simiilcr struc- 

 tures is the so-called derixed »;-t\pe.' The simplest forms of derived 



2 

 -JWWV- 



z, 



mZ, 



2 



KiK. *) - Miil-Scrifs Kqiiiv.ilent w-Ty|M; i)f Section 



Structures are shown in Kigs. '.t and 10. The structure of Fig. 9 

 has the same mid-series image impeti.ince as that shown in Fig. 2 

 and the value of this impedance is given b\- equation (6). The 

 structure of Fig. 10 has the siime mid-shunt image impedance as the ir 

 structure shown in I'ig. 4 and (he \alue of this impi-dance is gi\en by 



111 



TnZ, 



l-m' 



Hi 



I-'in. m MldSluiiit K(|iiiv,ilt'nt m- Tyiic of Section 



e<|u.iiion (7). On account (»f this identity of the respective mid-scrics 

 and the mid-slumt im.ige imintlances in the two cases, the structures 

 shown in Figs. 9 and 10 are calliil, respectively, the mid-series eqtiiva- 

 Init (Irrivnl »/-type and the mid-sliiinl equivalent derived 7H-type. The 

 7' and r structures «)f Figs. 2 ami 4 are called, respectively, the prolo- 

 lyprs n( the (leri\f<l wi-slructures of Figs. 9 an<l 10. In a series- 

 shunt filter com|)ose<i of sections of I he w-lype of l"ig. 9 or I'ig. 10, 



